Low-temperature tensile properties and average coefficients of linear expansion from low to ambient temperature were obtained for materials applicable to rocket engines including aluminum-, nickel-, iron-, copper- and titanium-base alloys and plastics. Procedures and techniques for tension and expansion coefficient testing at liquid hydrogen temperature (−423 F) and descriptions of testing chambers are given. Some alloys tested showed very high tensile strength while maintaining good ductility at liquid hydrogen temperature. Alloys considered suitable for use with liquid hydrogen include wrought and cast aluminum, nickel, copper and 9310 and A 286 steel. In general, coefficients of linear expansion decreased as temperatures approached that of liquid hydrogen.